The insertNodeInto method doesn't work for my JTree

Initially, I have a data set stored in the database and a BLANK JTree. This data set contains a tree structure, e.g.:
1. Documents
1.1 Correspondence
1.1.1 Incoming
1.1.2 Outgoing
1.2 Contracts
etc.

What I need, is to build the JTree based on the above-shown information. The problem is that insertNodeInto doesn't work properly in my code - only second-level nodes are added to the root node, while the path to the other nodes is not found. Where is the problem? Thanks!

The child node Contracts is added to the parent node Documents
The child node Correspondence is added to the parent node Documents
The path to the parent node Correspondence cannot be found.
The path to the parent node Correspondence cannot be found.
The child node Inner documents is added to the parent node Documents
The child node Labour contracts is added to the parent node Documents

For instance, hierarchy[1] (Correspondence) is a child of hierarchyChildOf[2] (Documents). Now I must populate JTree with these data. The task is just to add all nodes defined in hierarchy[] to corresponding parent nodes specified in hierarchyChildOf[].